A kinematic reconstruction of Iberia using intracontinental strike‐slip corridors

Despite considerable progress in restoring rifted margins, none of the current kinematic models can restore the Mesozoic motion of the Iberian block in full agreement with the circum‐Iberian geology. This conflict requires a revision of the kinematic description at the onset of divergence. The circum‐Iberian region has a unique geological dataset that allows calibration and testing of kinematic reconstructions and therefore it is an ideal candidate for testing intracontinental restoration approaches. Here we define intracontinental deforming regions, referred to as strike‐slip corridors, based on alignments of Mesozoic rift basins and/or transfer zones bordering rigid continental blocks. We use these strike‐slip corridors and data from the southern N‐Atlantic and Tethys to define the motion path of the Flemish Cap, Ebro and Iberia continental blocks. The resulting Mesozoic kinematic model for the Iberian block is compatible with recently published data and interpretations describing the Mesozoic circum‐Iberian geology. Large‐scale intracontinental strike‐slip corridors may offer a valid boundary condition for reconstructing continental block motion at the onset of divergence in intracontinental settings.


| INTRODUC TI ON
Great efforts have been directed recently in the plate kinematic community to consider the pre-breakup evolution in kinematic reconstructions of divergent plate boundaries (Aslanian & Moulin, 2013; Nirrengarten et al., 2018;Peace et al., 2019). A robust kinematic description appears crucial to a physics-based understanding of rifting (Brune et al., 2014;Gueydan et al., 2008;Williams et al., 2019). Kinematic restoration of divergent plate boundaries relies on a common procedure, which includes: (a) tight fit of seafloor magnetic anomalies, defining the position of diverging plates through time; (b) oceanic fracture zones, interpreted as flowlines, determining the direction of the motion; (c) necking zones, defining the tightest-fit solutions of reconstructions; and (d) paleomagnetic data from continental undeformed regions, outlining rotation and latitudinal shifts (Schettino & Turco, 2011).
This four-step approach has achieved outstanding results in reconstructing global plate motions at divergent settings . However, problems arise when obliquely deforming continental regions are considered, as shown for the Iberian case (Angrand et al., 2020;Tavani et al., 2018). During a large part of its Mesozoic history, Iberia was a continental rigid block delimited by intracontinental deforming regions, 40-200 km wide (Ady & Whittaker, 2019;Angrand et al., 2020;King et al., 2020) and hereafter referred to as strike-slip corridors. The M-series magnetic anomalies fringing Iberia on its N-Atlantic side have been shown to not represent classical oceanic magnetic anomalies and therefore to be unreliable for reconstructions (Nirrengarten et al., 2017;Szameitat et al., 2020). Moreover, kinematic reconstructions proposed Late Cretaceous subduction east of Iberia not harmonizing with tomographic data in the Pyrenees (Chevrot et al., 2018;Gong et al., 2008;Neres et al., 2012;Nirrengarten et al., 2017;Vissers & Meijer, 2012b).
The Mesozoic left-lateral motion of Africa (AFR) relative to Europe (EU) occurred while Iberia was diverging from North America (NAM) and interleaved rigid continental blocks were moving . We identify strike-slip corridors limiting rigid continental blocks, which include the Newfoundland, Flemish Pass, and Bay of Biscay-Iberian Rift corridors. Continental blocks are considered rigid if their internal estimated deformation is <30 km, that is, the error value introduced in restorations (Nirrengarten et al., 2018).
The motion of blocks is assumed to be perpendicular to necking lines at orthogonal intracontinental rifts or parallel to the dominant trend of strike-slip corridors. Relying on these corridors as motion paths for kinematic restorations enable to build a new kinematic model for the southern N-Atlantic and the Bay of Biscay, and to reconstruct the kinematics of Iberia from 200 to 83 Ma, that is, from Late Triassic onset of rifting in the Central Atlantic to Anomaly C34, the first unambiguous oceanic magnetic anomaly in the southern N-Atlantic.  Favre & Stampfli, 1992). Significant ~N-S directed extension is invoked after 126 Ma between Ebro and Europe (Jammes et al., 2009;Lescoutre and Manatschal, 2020;Tavani et al., 2018).

| ME THOD
The kinematic model proposed here is designed to respect boundary

| The Iberia-Europe-Ebro region
In our kinematic model, the lateral motion of IB relative to EBR is: with values inferred from hyperextended basins in the Pyrenees (e.g., Quintana et al., 2015;Teixell, 1998) and with post-83 Ma inferred N-S Alpine shortening in north Iberia (Macchiavelli et al., 2017;Wang et al., 2016).

| The southern N-Atlantic
Although the southern N-Atlantic provides some first-order input in our model, due to the existence of a complete data set, including reflection, refraction seismic data and ODP boreholes, our model also has some outputs that can be tested in this region. The validity of the reconstruction is supported by the parallelism between the computed FL-IB motion path and the trend of the displacement zone shown by Mohn et al. (2015) and interpreted as Lower Cretaceous (Figure 1).
Similarly, the reconstructed Jurassic IB-AFR motion path is parallel to displacement zones inferred by Fernández et al. (2019). Both structural trends fit with the motion path and confirm the validity of our approach (Figure 1).

| Strike-slip corridors: A new approach to restore pre-breakup rigid blocks
The kinematic reconstruction of Iberia prior to magnetic anomaly C34 is problematic due to the absence of large-scale, restorable marker features such as oceanic fracture zones or well defined oceanic magnetic anomalies, and because plate separation occurred during the magnetic quiet period (e.g. Cretaceous Normal Superchron) (Nirrengarten et al., 2017). Here we use intra-continental strike-slip corridors to assess the kinematic framework during continental

| Open questions
Three intriguing issues arise from the kinematic reconstruction (Data Repository S4, S5). The first issue regards gaps and overlaps in the

| Differences with previous kinematic reconstructions
The reconstruction of the southern N-Atlantic was traditionally based on two end-member approaches. A first group used the M-series magnetic anomalies as isochrons (Rowley & Lottes, 1988;Sibuet et al., 2004;Vissers & Meijer, 2012b

| CON CLUS IONS
The key point of the present reconstruction of Iberia is the definition of motion paths using strike-slip corridors, mainly marked by alignments of laterally confined and narrow rift basins or transfer zones. The resulting reconstruction of Iberia conforms at a first order with the circum-Iberian regional geology, suggesting that intracontinental strike-slip corridors may be used as a robust boundary condition to restore large rigid blocks back to the onset of rifting.

ACK N OWLED G EM ENTS
The authors thank B. Petri and S. Tomasi for discussions. GF and GM were supported by M5 consortium. PC, JM, RL, and GM were supported by OROGEN Project. Constructive reviews by Alexander Peace, Ruth Soto, Tony Doré and the Associate Editor helped to improve the manuscript.

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available in the supplementary material of this article. Note that the solution by Nirrengarten et al. (2018) is influenced east of Iberia by the use of the global plate kinematic framework of Seton et al. (2012). Note that Europe is fix in the sketch but the arrows south of Iberia represent the relative motion between Iberia and Africa. Thick red lines represent subduction zones [Colour figure can be viewed at wileyonlinelibrary.com]